Systematic Reviews & Evidence Synthesis Methods

A systematic review gathers, assesses, and synthesizes all available empirical research on a specific question using a comprehensive search method with an aim to minimize bias.

Or, put another way: 

A systematic review begins with a specific research question.  Authors of the review gather and evaluate all experimental studies that address the question.  Bringing together the findings of these separate studies allows the review authors to make new conclusions from what has been learned.

*The key characteristics of a systematic review are:

• A clearly stated set of objectives with pre-defined eligibility criteria for studies;
• An explicit, reproducible methodology;
• A systematic search that attempts to identify all relevant research;
• A critical appraisal of the included studies;
• A clear and objective synthesis and presentation of the characteristics and findings of the included studies.

*Lasserson TJ, Thomas J, Higgins JPT. Chapter 1: Starting a review [last updated August 2021]. In Higgins JPT, Thomas J, Chandler J, Cumpston M, Li T, Page MJ, Welch VA (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.5. Cochrane, 2024. Available from www.training.cochrane.org/handbook.

What is the difference between an evidence synthesis and a systematic review?
A systematic review is a type of evidence synthesis.  Any literature review is a type of evidence synthesis.  For the various types of evidence syntheses/literature reviews, see the page on this guide Types of Reviews.

Systematic reviews are usually done as a team project, requiring cooperation and a commitment of (lots of) time and effort over an extended period. You will need at least 3 people and, depending on the scope of the project and the size of the database result sets, you should plan for 6-24 months from start to completion